1. Field of the Invention
The invention relates to leveling apparatus, and more particularly to a leveling device for displaying to a high degree of precision a numerical readout of the deviation from the horizontal or vertical.
2. Description of the Prior Art
Leveling devices are known in the prior art where the sensing element is a conventional arcuate bubble level. The bubble level comprises a glass vial partially filled with a liquid and having an air gap therein whose position responds to the inclination of the level. One specific application is the common use as a carpenter's level where such a vial is embedded in a linear member which provides the reference plane and is aligned with the surface to be leveled. Another such device uses a bubble level hooked to a string stretched between two points to establish a level or grade. A hand-held sight glass has also been used in combination with a calibrated bubble level for quick field observations. In the prior applications, such a level would have graduations etched thereon to define the deviation from horizontal or vertical surfaces to which the level was applied. However, these devices are relatively inaccurate due to the lack of precise angular calibration, and because they require visual interpretation by the observer of the position of the bubble with respect to the graduations. It is clear that this interpretation may vary from one observer to another, and over a period of time. Other means of measuring the levelness or adjusting a surface to a desired grade or angle include geometric instruments, such a surveyor's optical transit, but such devices are cumbersome and time consuming to use, although capable of providing a high degree of precision. Further, such instruments require an expertise that is not possessed by the layman, or indeed, the ordinary skilled craftsman. Moreover, scales such as used on a transit are susceptible to human error in reading, since they are essentially analog in nature and may require vernier interpolation.